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Here we describe a new subgenus and three new species of parasitic water mites in the genus Unionicola (Acari: Hydrachnidia) from Myanmar: Myanmaratax subgen. nov., Unionicola (Myanmaratax) savadiensis subgen. and sp. nov. (hosts: Lamellidens savadiensis and L. generosus), U. (My.) generosa sp. nov. (the same hosts), and U. (My.) trapezidenssp. nov. (hosts: Trapezidens dolichorhynchus and T. angustior). These taxa were identified based on a two-gene phylogenetic analysis (COI + 28S), which also confirms the division of the genus Unionicola into numerous subgenera. The new species are cryptic species, which are morphologically indistinguishable but strongly resemble U. (Prasadatax) brandti Vidrine, 1985 described from Thailand (hosts: Lens spp. and Ensidens spp.). We also transfer the latter taxon from Prasadatax to Myanmaratax based on a set of morphological evidence and propose U. (My.) brandti comb. nov. The new subgenus contains a total of five species, one of which needs future sampling efforts and will be described elsewhere. Additionally, 56 valid subgenera, which were placed in the synonymy of the genus and in one case raised to the genus level, are restored here until robust phylogenetic evidence on their taxonomic status is available. Our results also confirm that Unionicola mites are narrow host specialists that are associated with either one or a few closely related freshwater mussel species belonging to one or two sister genera. [ABSTRACT FROM AUTHOR]

Multiparasitism by different species of larval water mites was observed on an adult midge collected in Hokkaido, northern Japan. Water mite larvae of Hygrobates sp. and Unionicola sp. in an inactive stage were discovered from a single chironomid female in the subfamily Chironominae. Eight Hygrobates larvae parasitized on the dorsum, and four were on the venter from the first to fourth abdominal segments of the midge. One Unionicola larvae attached on the trochanter of the left midleg and one on the femur of the right midleg. Their attachment sites on the midge accorded well with the larval site preferences of these two genera, as reported in past studies. Considering the preference of Unionicola for the specific segments of the legs, the observed site partitioning between Hygrobates and Unionicola seems to have originated by intrinsic site preferences of each taxon rather than interspecific competition. On the other hand, two less-engorged Hygrobates larvae were observed among the fully engorged larvae on the abdominal segments of the midge. Such developmental variations are possibly caused by intraspecific competition for nutrients among conspecific larvae on a single host individual. [ABSTRACT FROM AUTHOR]

Here we describe a new subgenus and three new species of parasitic water mites in the genus Unionicola (Acari: Hydrachnidia) from Myanmar: Myanmaratax subgen. nov., Unionicola (Myanmaratax) savadiensis subgen. and sp. nov. (hosts: Lamellidens savadiensis and L. generosus), U. (My.) generosa sp. nov. (the same hosts), and U. (My.) trapezidenssp. nov. (hosts: Trapezidens dolichorhynchus and T. angustior). These taxa were identified based on a two-gene phylogenetic analysis (COI + 28S), which also confirms the division of the genus Unionicola into numerous subgenera. The new species are cryptic species, which are morphologically indistinguishable but strongly resemble U. (Prasadatax) brandti Vidrine, 1985 described from Thailand (hosts: Lens spp. and Ensidens spp.). We also transfer the latter taxon from Prasadatax to Myanmaratax based on a set of morphological evidence and propose U. (My.) brandti comb. nov. The new subgenus contains a total of five species, one of which needs future sampling efforts and will be described elsewhere. Additionally, 56 valid subgenera, which were placed in the synonymy of the genus and in one case raised to the genus level, are restored here until robust phylogenetic evidence on their taxonomic status is available. Our results also confirm that Unionicola mites are narrow host specialists that are associated with either one or a few closely related freshwater mussel species belonging to one or two sister genera.

Abstract Background The aquatic Acari are known as water mites and occupy a wide range of habitats. The freshwater mites, Unionicola aegyptiaca, were collected from the freshwater mussel, Caelatura aegyptiaca, River Nile, Sohag, Egypt. The present paper focuses on the structure of the cuticle and musculature of freshwater mite, U. aegyptiaca. Results Histologically, the cuticle consists of two main layers: epicuticle and procuticle. The latter divided into two sublayers, exocuticle (exo) and endocuticle (en). The musculature of the present species, U. aegyptiaca, is divided into three regions: gnathosoma, idiosoma, and legs. The muscles of the body are classified according to their position and function. Conclusion Details of muscles of gnathosoma, coxal epimerae, genital field, and legs were all described and discussed. The cuticle and musculature of U. aegyptiaca were studied by using the light microscope, and the drawings were down with the help of a camera Lucida. It is likely to note that the cuticle and musculature of freshwater mite, U. aegyptiaca, were described and discussed for the first time in Egypt.

Water mites of the genus Unionicola are common parasites of freshwater mussels, living on the gills or mantle of their hosts and using these tissues as sites of oviposition. Although surveys of this mite fauna among North American unionid mussels indicate that these mites represent highly diverse assemblages, we know very little regarding the determinants of Unionicola species diversity among their molluscan hosts. The present study addresses the relationship between host diversity and mite diversity for Unionicola assemblages associated with unionid mussels of North America. The results of this study found a significantly positive relationship between host species richness and mite species richness, adding to a growing body of evidence that host diversity is an important determinant of parasite diversity. In recent years, molecular sequence data have discovered cryptic biodiversity among unionid mussels, yielding revisions in the nomenclature and systematic taxonomy of the group. DNA sequence variation has also revealed cryptic species complexes among Unionicola mites. Collectively, these findings suggest that the results of the present study may be underestimating species richness among mites and their host mussels. Unfortunately, human perturbations are known to have caused high recent rates of extinction in the mussel and mite faunas of North America and could play a major role in influencing patterns of species richness for this host–parasite system moving forward. [ABSTRACT FROM AUTHOR]

Background: The aquatic Acari are known as water mites and occupy a wide range of habitats. The freshwater mites, Unionicola aegyptiaca, were collected from the freshwater mussel, Caelatura aegyptiaca, River Nile, Sohag, Egypt. The present paper focuses on the structure of the cuticle and musculature of freshwater mite, U. aegyptiaca. Results: Histologically, the cuticle consists of two main layers: epicuticle and procuticle. The latter divided into two sublayers, exocuticle (exo) and endocuticle (en). The musculature of the present species, U. aegyptiaca, is divided into three regions: gnathosoma, idiosoma, and legs. The muscles of the body are classified according to their position and function. Conclusion: Details of muscles of gnathosoma, coxal epimerae, genital field, and legs were all described and discussed. The cuticle and musculature of U. aegyptiaca were studied by using the light microscope, and the drawings were down with the help of a camera Lucida. It is likely to note that the cuticle and musculature of freshwater mite, U. aegyptiaca, were described and discussed for the first time in Egypt. [ABSTRACT FROM AUTHOR]

Water mites of the genusUnionicolaHaldeman, 1842 are common symbionts of freshwater mussels, living on the gills or mantle and foot of their hosts, and using these tissues as sites of oviposition. Cryptic species – two or more distinct species that have been designated as a single species – in this instance, genetically differentiated host-associated populations that are difficult to distinguish morphologically – have been reported for these mites; however, the extent to which they typify the genus is not well known. As part of an ongoing study characterizing cryptic biodiversity amongUnionicolamussel-mites, we examined sequence divergence in the mitochondrial cytochrome oxidase subunit I (COI) gene among populations ofUnionicola hoeseiVidrine, 1986, a gill mite that is known to occur in association with many species of host mussels, and compared these data to those reported for otherUnionicolacryptic species complexes. Genetic distance data revealed that four populations ofUnionicola hoeseiexhibited p-distances that are consistent (; range = 0.08–0.17) with those reported for cryptic species ofUnionicola. A phylogenetic hypothesis for the populations ofUn. hoeseiin relation to other cryptic species of mussel-mites was constructed using neighbour-joining analysis. The gene tree indicated that host-associated populations ofUn. hoesei, like other cryptic species of the genus, formed a distinct clade, whose branches mainly reflect their association with different species of host mussels. The results of this study raise questions about the patterns of host utilization among other populations ofUn. hoeseireported from additional species of North American mussels. Future studies will compare heterogeneity in DNA sequence data among populations ofUn. hoeseifrom a large number of host species, both locally and over a broad geographic range, to determine the degree to which genetic variability exhibited by these mites is structured geographically and by patterns of host use. [ABSTRACT FROM AUTHOR]

Unionicola (Wolcottatax) arcuata (Wolcott, 1898) (Acari: Hydrachnidia: Unionicolidae) commonly occurs in parasitic association with Cristaria plicata (Leach), Anodonta woodiana elliptica (Heude) or Anodonta woodiana pacifica (Heude) during one or more stages of its life cycle. The mitochondrial 12S rRNA gene was sequenced and analysed from U. arcuata obtained from nine populations of these freshwater mussels from six large lakes in the middle and lower reaches of the Yangtze River, China. The 382 base sequence alignments for these nine populations of U. arcuata had two gaps and contained 51 (13.4%) variable nucleotides. The pairwise divergences among U. arcuata sequence data ranged from 0 to 10.9%, with the lowest intraspecific divergences (0–0.5%) observed among U. arcuata obtained from the same host species and the highest intraspecific divergences (6.7–10.9%) found among U. arcuata from different species of hosts. The results of sequence alignment and divergence were consistent with the heterogeneity in sequence data of the 12S rRNA gene observed in other studies of acarines. Maximum parsimony and maximum likelihood analyses each yielded a single tree with the same topology and high bootstrap support. The gene trees indicate three major clades, with U. arcuata from C. plicata, A. woodiana elliptica and A. woodiana pacifica each forming a distinct clade. Overall, the results of this study indicated that host association, rather than patterns of geographic distribution, plays an important role in the degree of genetic divergence among populations of U. arcuata. [ABSTRACT FROM AUTHOR]

The morphological features, the measurements and drawings of various organs and the geographical distributions of Neumania (s.str.) imitata Koenike, 1908, N. (s.str.) uncinata Walter, 1927 and Unionicola (Majumderatax) hankoi (Szalay, 1927) are given. N. (s.str.) imitata Koenike, 1908 is a new record for the Turkish fauna. [ABSTRACT FROM AUTHOR]

The mitochondrial genome of Unionicola foili is circular, 14,738 bp in length, and contains several notable features. The sequence and annotation revealed a unique gene order, continuing a pattern of highly rearranged mitochondrial genomes in the Trombidiformes. U. foili mitochondrial tRNA sequences predict non-canonical secondary structures for these molecules, and our annotation suggests an in-frame fusion between the nad4L and nad5 genes in this genome. The unique gene order and unusual tRNA structures could serve as idiosyncratic characters and have the potential to be phylogenetically informative. [ABSTRACT FROM AUTHOR]

Descriptions and figures of two new sympatric species of water-mites, Unionicola blayi and U. planicurvata, belonging to a new unionicoline subgenus, Mutelicola, found in the mutelid bivalve Aspatharia sinuata (von Martens, 1883) in Nigeria are presented. These are the first records of unionicoline 'parasites' of bivalves from Africa and the first records of unionicolines from mutelid mussels. Their occurrence in these freshwater bivalves is discussed and some data on unionicoline-bivalve relationships are also presented. [ABSTRACT FROM AUTHOR]